Sucralfate in the digestive tract reacts with gastric acid to form a bio-adhesive gel which adheres to the mucous membrane of the digestive tract, thereby creating a local protective barrier. At the inflammatory or ulcer site, the protective barrier protects the mucous membrane of the digestive tract from excessive gastric acid and the like and promotes the ability of the human body to repair the mucous membrane of the stomach, thereby exhibiting a healing effect. In expectation of its ability to protect the mucous membrane of the stomach, sucralfate is administered simultaneously with various drugs at the medical setting.
However, depending on the drug to be administered simultaneously with sucralfate, the bio-adhesive gel composition formed of the sucralfate will adsorb the drug, trap it within the gel composition, form a complex or be subject to other adverse effects that either prevent or retard the absorption of the drug itself. To mention a few examples of the cases that have been reported on these phenomena, Brouwers et al. reported in 1990 that Tmax, Cmax, AUC and bio-availability of ciprofloxacin dropped significantly when used in combination with sucralfate (Drug Invest., 2(3):197, 1990); in the same year, Lafontaine et al. reported delayed absorption of naproxen due to simultaneous administration of sucralfate (Clin. Pharm., 9(10):773, 1990); Cantral et al. reported reduced AUC of theophylline due to sucralfate (Clin. Pharm., 7(1):58, 1988); Anaya et al. reported delayed absorption of ibuprofen due to simultaneous administration of sucralfate (Biopharm. Drug Dispos., 7(5):443, 1986); Maconochie et al. reported reduced AUC and Cmax levels of ranitidine due to simultaneous administration of sucralfate (Clin. Pharmacol. Ther., 41(2):205, 1987); and Yoshida et al. reported reduced AUC of cimetidine due to simultaneous administration of sucralfate (Journal of the Society of Gastrointestinal Diseases of Japan, 84(5):1025, 1987).
The beecham Group Public Limited Company filed Japanese Patent Application No. 500445/1992, in which they took advantage of the adsorptive action of sucralfate in ensuring the local sustained release of H.sub.2 antagonists.
Although it is known that when sucralfate is incorporated or administered simultaneously with other drugs, it adsorbs, traps or otherwise affects the drugs to potentially interfere with their absorption, few proposals have been made offering effective methods and means for avoiding the problem. In the actual medical setting, some provisions are necessary such as the avoidance of combined use of sucralfate and other drugs or sequential administration of the two drugs with a certain time interval being allowed; thus, it has been difficult to secure the high bioavailability of drugs when they are administered simultaneously with sucralfate.